How make a simple hover?

[Zephyr]

? ? ?

[Jovis]

The easiest way to make a craft that hovers is to place enough balloon deployers to lift your craft, and add two automated control blocks.
Set one to below altitude [lowest altitude you want your craft to fly,] deploy balloons,
and the other to above altitude [Highest altitude you want your craft at] deactivate balloons.
Hope this helps!

[An Ning]

I don't usually count balloons as "hovercraft", myself -though I suppose others might.

ACBs, though, are the general answer to all things hover.

For hovercraft using ion or jet engines, place the engines with exhaust facing down, press "q" and set them to "main"
Then, above the engines, place 2 ACBs, 1 set to turn propulsion to 1 (full power) below a set altitude, and another to set propulsion to 0 (no power) above another altitude.
Be sure to reduce the effect distance of each ACB so it doesn't stop the engines you use for thrust as well.

The benefit to this is that you can make relatively small and compact hovercraft. The downside is they tend to use a lot of power, and the engines are difficult to leave unexposed as they do not work if completely contained.


Here is an example of a jet and ion hovercraft. You can take it apart to see how it works, it's pretty simple overall.
http://steamcommunity.com/sharedfiles/filedetails/?id=691967066




For hovercraft using rotors, it's pretty similar. You place a dedicated spinner with the blades, and set the ACBs to activate spinblocks above and below a certain altitude.

There are things to note, though.
First is that you can set the "engine power" that the spinner uses, increasing or decreasing lift based on power draw.
Next is the "always up faction", this will set the blades so they will either push/pull based on the direction they are facing or spinning, or always pull up regardless of how they are facing or spinning
--Without this, blades facing up with a positive spin will pull up, and a negative spin will push down (and inverse with blades facing down). This also means that as your ship rolls, the blades pull in the direction of the roll, meaning you lose lift and fall a bit. Using it, however, means that your blades will ALWAYS pull your ship "up"... even if you tip upside-down... which can be infuriating

The main advantage to rotors is that they can be enclosed, also they can be overlapped (see the Cockatrice in DWG builds).
They require a lot of room, but are good at carrying a large load.

here is an example of a larger rotor-based hovercraft:
http://steamcommunity.com/sharedfiles/filedetails/?id=693249419




Ragardless, hovercraft are notoriously unstable.
Small ones can be forced into climbs and descents by the AI utilizing roll thrusters or rotors if they are not almost perfectly balanced, and larger ones are incredibly "tippy", requiring other main thrusters set to activate at certain pitch and roll angles.

here is an example of a rotor-craft that uses jet enjones to stabilize its pitch
http://steamcommunity.com/sharedfiles/filedetails/?id=726266133



Here is a rotor-based hovercraft that uses positive and negative spins to control both pitch and altitude:
http://steamcommunity.com/sharedfiles/filedetails/?id=731218384





There is another type of hovercraft that I rarely see employed. It uses a naval AI (whereas all the others here are aerial AI) and relies on masses of water propellers beneath the craft facing downward to skim the top of the water.

It is simpler and more stabile (in general) than the other hovercraft, but must remain in water to be used.

[Takamiki]

using dedicated heliblades is the best i find i made a hover tank that stays at 10 meters and it doesn't flip due to thruster PIDs controlling pitch and roll

[capnguts]

If you go the route of 'Always Up' on heli spinners and mount them near the top of your craft, you can essentially let your craft hang down from its spinners, largely negating the need for pitch and roll control.

[Fatboychummy]

You can also set up an AI aerial Altitude PID to get a VERY stable, no fluctuation hovercraft.